The invention relates to a bumper for a motor vehicle.
Bumpers are commonly installed on the front and on the rear of motor vehicles to absorb the impact energy caused by small impacts, thereby minimizing damage to the actual support structure of the motor vehicle. A bumper is typically constructed of a cross member which can be attached to the longitudinal rails of the motor vehicle frame by incorporating crash boxes. The cross member operates to transmit the energy resulting from an impact into the crash boxes, where the impact energy is converted into deformation energy. The system is matched by locating the crash boxes as close to the center of longitudinal rail of the motor vehicle as possible, wherein the impact energy is transmitted via the cross member into the crash boxes and hence into the longitudinal rails with minimum bending moment.
Various bumpers of different designs are known in the art. For example, U.S. Pat. No. 6,349,521 B1 discloses a conventional bumper with a rigid cross member configured as a hollow support. The cross-section varies over the length of the cross member in order to provide the cross member with a high energy absorption capability commensurate with the load.
EP 1 730 002 B1 discloses a bumper with a cross member having a U-shaped longitudinal profile that is closed off with a cover plate. The cross member known from EP 1 182 095 B1 is constructed from an upper shell and a lower shell which face one another and are connected at front faces of front legs along overlapping longitudinal sections.
EP 1 495 917 B1 discloses a bumper with a cross member having a lower section and an upper section, wherein the upper section protrudes outwardly with respect to the lower section and includes a shock absorber. The lower section is stiffened by a reinforcement element. Additional examples of bumpers and/or bumper systems are given in DE 10 2007 001 966 A1 or DE 10 2004 055 518 A1.
In addition to the regulatory requirements which are part of the type approval in Europe, consumer protection agencies, such as Euro-NCAP, also evaluate on new vehicles the protection of pedestrians. In addition, the requirements stipulated by the insurers' classification test (Research Council for Automobile Repairs (RCAR), Gesamtverband der deutschen Versicherungswirtschaft (German Insurance Association) (GDV)) must also be met. Automobile manufacturers typically also demand optimal utilization of the installation space, ease of installation, high energy absorption capability as well as lowest possible weight and acceptable costs.
The current discussion of reducing CO2-emission in the automobile industry requires a consequent implementation of lightweight construction in vehicle development. However, the required weight reduction and the insurance classification tests contradict one another. In these tests, collisions of the bumpers or bumper systems with barriers are performed at different speeds. Cross members designed for RCAR/GDV tests are frequently 20-30% heavier than conventional systems, because minimum geometric requirements are set and the supports must have substantial height to meet the test requirements. Nonetheless, overriding or underriding a barrier can frequently not be prevented at all or only with great difficulty, depending on the vehicle type, in spite of the minimum geometric requirements. The design of the vehicle frequently also prevents an optimal configuration of the cross member.
Based on the state of the art, it is therefore an object of the invention to improve the functionality of a lightweight bumper and to increase its energy absorption capability in the overall concept of a bumper system.